Networking Definitions

This glossary explains the meaning of key words and phrases that information technology (IT) and business professionals use when discussing networking and related software products. You can find additional definitions by visiting WhatIs.com or using the search box below.

  • O

    OSI model (Open Systems Interconnection)

    OSI (Open Systems Interconnection) is a reference model for how applications communicate over a network.

  • OSPF (Open Shortest Path First)

    The OSPF router protocol is used to find the best path for packets as they pass through a set of connected networks. OSPF is one of several Interior Gateway Protocols that replaces the Routing Information Protocol (RIP), an older routing protocol that is installed in many of today's corporate networks.

  • over-the-top (OTT)

    Over-the-top (OTT) is networking lingo that describes the delivery of content, services or applications over the internet.

  • overlay network

    An overlay network is a telecommunications network that is built on top of another network and is supported by its infrastructure.

  • OVSDB (Open vSwitch Database Management Protocol)

    The Open vSwitch Database Management Protocol (OVSDB) is an OpenFlow configuration protocol that is designed to manage Open vSwitch implementations.

  • P

    packet filtering

    On the Internet, packet filtering is the process of passing or blocking packets at a network interface based on source and destination addresses, ports, or protocols.

  • packet loss

    Packet loss is when one or more transmitted data packets fail to arrive at their destination.

  • passive optical network (PON)

    A passive optical network (PON) is a system commonly used by telecommunications network providers that brings fiber optic cabling and signals all or most of the way to the end user.

  • patch panel

    A patch panel in a local area network (LAN) is a mounted hardware assembly that contains ports that are used to connect and manage incoming and outgoing LAN cables.

  • peer-to-peer (P2P)

    Peer-to-peer (P2P) is a decentralized communications model in which each party has the same capabilities and either party can initiate a communication session.

  • permanent virtual circuit (PVC)

    A permanent virtual circuit (PVC) is a software-defined logical connection in a network such as a frame relay network.

  • phase-locked loop (PLL)

    A phase-locked loop (PLL) is an electronic circuit with a voltage or voltage-driven oscillator that constantly adjusts to match the frequency of an input signal.

  • physical layer

    Located at the lowest layer of the Open Systems Interconnection (OSI) communications model, the physical layer's function is to transport data using electrical, mechanical or procedural interfaces.

  • ping

    A ping (Packet Internet or Inter-Network Groper) is a basic internet program that enables a user to test and verify if a particular destination Internet Protocol (IP) address exists and can accept requests in computer network administration.

  • ping sweep (ICMP sweep)

    A ping sweep (also known as an ICMP sweep) is a basic network scanning technique used to determine which of a range of IP addresses map to live hosts (computers).

  • Plain Old Telephone Service (POTS)

    Plain Old Telephone Service (POTS) refers to the traditional, analog voice transmission phone system implemented over physical copper wires (twisted pair).

  • point-of-presence (POP)

    On the Internet, a point-of-presence (POP) is an access point from one place to the rest of the Internet.

  • Point-to-Point Protocol over Ethernet (PPPoE)

    Point-to-Point Protocol over Ethernet (PPPoE) is a network protocol that facilitates communication between network endpoints.

  • poison reverse

    In a computer network that uses the Routing Information Protocol (RIP) or other distance vector routing protocol, poison reverse is a loop avoidance process.

  • policy-based networking

    Policy-based networking is the management of a network so that various kinds of traffic - data, voice, and video - get the priority of availability and bandwidth needed to serve the network's users effectively.

  • port

    A port in computing has three main uses, each as a type of receptacle in networking, computer hardware and software.

  • port 80

    On a Web server or Hypertext Transfer Protocol daemon, port 80 is the port that the server "listens to" or expects to receive from a Web client, assuming that the default was taken when the server was configured or set up.

  • Port Address Translation (PAT)

    Port Address Translation (PAT), is an extension to network address translation (NAT) that permits multiple devices on a local area network (LAN) to be mapped to a single public IP address. The goal of PAT is to conserve IP addresses.

  • port mirroring (roving analysis port)

    Port mirroring is an approach to monitoring network traffic that involves forwarding a copy of each packet from one network switch port to another.

  • port number

    Port number is a way to identify a specific process to which an internet or other network message is to be forwarded when it arrives at a server.

  • Power over Ethernet (PoE)

    Power over Ethernet (PoE) is a technology for implementing wired Ethernet local area networks (LANs) that enables the electrical current necessary for operating each device to be carried by Ethernet data cables instead of standard electrical power cords and wiring.

  • POX

    POX is an open source development platform for Python-based software-defined networking (SDN) control applications, such as OpenFlow SDN controllers.

  • PPP (Point-to-Point Protocol)

    PPP (Point-to-Point Protocol) is a standard used to establish a direct connection between two network nodes that enables the transport of multiprotocol data.

  • preboot execution environment (PXE)

    Preboot execution environment (PXE), pronounced pixie, is a set of standards that enables a computer to load an operating system (OS) over a network connection.

  • presentation layer

    Residing at Layer 6 of the Open Systems Interconnection (OSI) communications model, the presentation layer ensures that the communications that pass through it are in the appropriate form for the recipient application.

  • private automatic branch exchange (PABX)

    A private automatic branch exchange (PABX) is an automatic telephone switching system within a private enterprise.

  • programmable network (PN)

    A programmable network is one in which the behavior of network devices and flow control is handled by software that operates independently from network hardware.

  • propagation delay

    Propagation delay is the amount of time required for a signal to be received after it has been sent; it is caused by the time it takes for the signal to travel through a medium.

  • PSTN (public switched telephone network)

    The public switched telephone network, or PSTN, is the world's collection of interconnected voice-oriented public telephone networks.

  • pulse code modulation (PCM)

    Pulse code modulation (PCM) is a digitalscheme for transmitting analogdata.

  • Q

    QAM (quadrature amplitude modulation)

    QAM (quadrature amplitude modulation) is a method of combining two amplitude modulation (AM) signals into a single channel.

  • R

    radio access network (RAN)

    A radio access network (RAN) is a major component of a wireless telecommunications system that connects individual devices to other parts of a network through a radio link.

  • radio frequency (RF, rf)

    Radio frequency (RF) is a measurement representing the oscillation rate of electromagnetic radiation spectrum, or electromagnetic radio waves, from frequencies ranging from 300 GHz to as low as 9 kHz.

  • Real-time Transport Protocol (RTP)

    Real-time Transport Protocol (RTP) is a network standard designed for transmitting audio or video data that is optimized for consistent delivery of live data.

  • registered port numbers

    The registered port numbers are the port numbers that companies and other users register with the Internet Corporation for Assigned Names and Numbers (ICANN) for use by the applications that communicate using the Internet's Transmission Control Protocol (TCP) or the User Datagram Protocol (UDP).

  • repeater

    In digital communication systems, a repeater is a device that receives a digital signal on an electromagnetic or optical transmission medium and regenerates the signal along the next leg of the medium.

  • Reverse Address Resolution Protocol (RARP)

    Reverse Address Resolution Protocol (RARP) is a protocol a physical machine in a local area network (LAN) can use to request its IP address.

  • reverse Telnet (direct Telnet)

    Reverse Telnet (sometimes called direct Telnet) is the initiation of a Telnet session from a computer system to one of its remote users.

  • ROADM (reconfigurable optical add-drop multiplexer)

    An ROADM (reconfigurable optical add-drop multiplexer) is a device that can add, block, pass or redirect modulated infrared (IR) and visible light beams of various wavelengths in a fiber optic network. ... (Continued)

  • round-trip time (RTT)

    Round-trip time (RTT), also called round-trip delay, is the time required for a signal pulse or packet to travel from a specific source to a specific destination and back again...(Continued)

  • route summarization (route aggregation)

    Route summarization -- also known as route aggregation -- is a method to minimize the number of routing tables in an Internet Protocol (IP) network.

  • router

    A router is a physical or virtual appliance that passes information between two or more packet-switched computer networks.

  • Routing Information Protocol (RIP)

    Routing Information Protocol (RIP) is a distance vector protocol that uses hop count as its primary metric.

  • routing table

    A routing table is a set of rules, often viewed in table format, that is used to determine where data packets traveling over an Internet Protocol (IP) network will be directed.

  • RS-232C

    RS-232C is a long-established standard ("C" is the current version) that describes the physical interface and protocol for relatively low-speed serial data communication between computers and related devices.

  • RSVP (Resource Reservation Protocol)

    RSVP (Resource Reservation Protocol) is a set of communication rules that allows channels or paths on the Internet to be reserved for the multicast (one source to many receivers) transmission of video and other high-bandwidth messages.

  • runbook

    Runbooks are a set of standardized written procedures for completing repetitive IT processes within a company.

  • S

    satellite news gathering (SNG)

    Satellite news gathering (SNG) is the use of mobile communications equipment for the purpose of worldwide newscasting.

  • SD-branch

    SD-branch is a single, automated, centrally managed software-centric platform that replaces or supplements an existing branch network architecture.

  • SD-WAN (software-defined WAN)

    Software-defined WAN (SD-WAN) is technology that uses software-defined networking (SDN) concepts to distribute network traffic across a wide area network (WAN).

  • SDN application (software-defined networking application)

    An SDN application is a software program designed to perform a task in a software-defined networking (SDN) environment. SDN applications can replace and expand upon functions that are implemented through firmware in hardware devices in a conventional networking environment.

  • SDN controller (software-defined networking controller)

    An SDN controller is an application in a software-defined networking (SDN) architecture that manages flow control for improved network management and application performance.

  • SDN overlay (software defined networking overlay)

    An SDN overlay is a deployment method for network virtualization and software-defined networking (SDN) that involves running a logically separate network or network component on top of existing infrastructure.

  • Secure Access Service Edge (SASE)

    Secure Access Service Edge, also known as SASE -- pronounced 'sassy' -- is a cloud architecture that bundles network and security solutions together and delivers them as a unified cloud service.

  • Seebeck effect

    The Seebeck effect is a phenomenon in which a temperature difference between two dissimilar electrical conductors or semiconductors produces a voltage difference between the two substances.

  • serial digital interface (SDI)

    Serial digital interface (SDI) is a standard for digital video and audio transmission over coaxial or fiber optic cabling.

  • Server Message Block protocol (SMB protocol)

    The Server Message Block protocol (SMB protocol) is a client-server communication protocol used for sharing access to files, printers, serial ports and other resources on a network.

  • Service Profile Identifier (SPID)

    In telecommunications, a Service Profile Identifier (SPID) is a number assigned by a phone company to a terminal on an Integrated Services Digital Network (ISDN) B-channel.

  • session border controller (SBC)

    A session border controller (SBC) is a dedicated hardware device or software application that governs the manner in which phone calls are initiated, conducted and terminated on a voice over Internet Protocol (VoIP) network.

  • Session layer

    In the Open Systems Interconnection (OSI) communications model, the session layer resides at Layer 5 and manages the setup and teardown of the association between two communicating endpoints.

  • session-based routing

    Session-based routing is a type of routing architecture that is application-centric and designed to route entire sessions instead of individual packets.

  • shielded twisted pair (STP)

    Shielded twisted pair (STP) is a special kind of copper telephone and local area network (LAN) wiring used in some business installations.

  • signal

    In electronics, a signal is an electric current or electromagnetic field used to convey data from one place to another.

  • signal-to-noise ratio (S/N or SNR)

    In analog and digital communications, a signal-to-noise ratio, often written S/N or SNR, is a measure of the strength of the desired signal relative to background noise (undesired signal).

  • Signaling System 7 (SS7)

    Signaling System 7 (SS7) is an international telecommunication protocol standard that defines how the network elements in a public switched telephone network (PSTN) exchange information and control signals.

  • Simple Network Management Protocol (SNMP)

    Simple Network Management Protocol (SNMP) is an application-layer protocol for monitoring and managing network devices on a local area network (LAN) or wide area network (WAN).

  • single-user MIMO

    Single-user MIMO (SU-MIMO) is a multi-transmitter and receiver technology that lets a wireless access point send multiple, simultaneous data streams to one compatible endpoint at a time.

  • sliding window (windowing)

    The sliding window (windowing) technique is used by Transmission Control Protocol (TCP) to manage the flow of packets between two computers or network hosts.

  • small cell

    A small cell is an umbrella term used to describe a miniature radio access point or wireless network base station with a low radio frequency power output, footprint and range.

  • Snort

    Snort is an open source network intrusion detection system (NIDS) created by Sourcefire founder and former CTO Martin Roesch.

  • software-defined networking (SDN)

    Software-defined networking (SDN) is an architecture that abstracts different, distinguishable layers of a network to make networks agile and flexible.

  • software-defined networking monitoring application (SDN monitoring application)

    An SDN monitoring application is a software program that oversees the traffic in a software-defined network (SDN) as a component of network management.

  • Spanning Tree Protocol (STP)

    Spanning Tree Protocol (STP) is a Layer 2 network protocol used to prevent looping within a network topology.

  • spectrum analyzer

    A spectrum analyzer is a device that measures and displays signal amplitude (strength) as it varies by frequency within its frequency range (spectrum).

  • split horizon

    Split horizon is a method used by distance vector protocols to prevent network routing loops.

  • spread spectrum

    Spread spectrum is a form of wireless communications in which the frequency of the transmitted signal is deliberately varied.

  • star network

    A star network is a local area network (LAN) topology in which all nodes -- personal computers (PCs), workstations or other devices -- are directly connected to a common central computer that is often referred to as a hub.

  • start of authority record

    A start of authority (SOA) record is information stored in a domain name system (DNS) zone about that zone and about other DNS records.

  • stateful inspection

    Stateful inspection, also known as dynamic packet filtering, is a firewall technology that monitors the state of active connections and uses this information to determine which network packets to allow through the firewall.

  • Stream Control Transmission Protocol (SCTP)

    Stream Control Transmission Protocol (SCTP) is a connection-oriented network protocol for transmitting multiple streams of data simultaneously between two endpoints that have established a connection in a network.

  • subcarrier

    A subcarrier is a secondary modulated signal frequency modulated into the main frequency (the carrier) to provide an additional channel of transmission.

  • subnet (subnetwork)

    A subnet, or subnetwork, is a segmented piece of a larger network.

  • subnetwork

    A subnetwork is a separately identifiable part of a larger network that typically represents a certain limited number of host computers, the hosts in a building or geographic area, or the hosts on an individual local area network.

  • Switched Multimegabit Data Service (SMDS)

    Switched Multimegabit Data Service (SMDS) is a public, packet-switched service aimed at enterprises that need to exchange large amounts of data with other enterprises over the wide area network on a nonconstant or bursty basis.

  • SYN scanning

    SYN scanning is a tactic that a malicious hacker can use to determine the state of a communications port without establishing a full connection.

  • Synchronous Data Link Control (SDLC)

    Synchronous Data Link Control (SDLC) is a transmission protocol used to synchronously transfer code-transparent, serial-by-bit data over a communications channel.

  • Synchronous Digital Hierarchy (SDH)

    Synchronous Digital Hierarchy (SDH) is a group of fiber optic transmission rates that transport digital signals with different capacities.

  • Synchronous Optical Network (SONET)

    Synchronous Optical Network (SONET) is a standard for synchronous data transmission on optical fibers.

  • system administrator (sysadmin)

    A system administrator (sysadmin) is an information technolog professional who supports a multiuser computing environment and ensures continuous, optimal performance of IT services and support systems.

  • T

    T-carrier system

    To see the relationship between T-carrier, E-carrier, and DS0 multiples, see digital signal X. The T-carrier system, introduced by the Bell System in the U.S. in the 1960s, was the first successful system that supported digitized voice transmission.

  • T1 (T-1)

    Also see the T-carrier system, of which the T1 is a part.

  • TCP/IP

    TCP/IP stands for Transmission Control Protocol/Internet Protocol and is a suite of communication protocols used to interconnect network devices on the internet.

  • telecommunications (telecom)

    Telecommunications, also known as telecom, is the exchange of information over significant distances by electronic means and refers to all types of voice, data and video transmission.

  • telematics

    Telematics uses GPS and mobile devices to send and receive information that helps control remote objects, primarily in the automotive industry.

  • Telnet

    Telnet is a network protocol used to virtually access a computer and to provide a two-way, collaborative and text-based communication channel between two machines.

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